Field of the Invention
The present disclosure relates to new block copolymers for inclusion in compositions that can be utilized for directed self-assembly pattern formation in the fabrication of microelectronic structures.
Description of the Prior Art
The increasing demand of smaller micro-fabricated devices requires a continuous decrease in the feature size of device components. Conventional photolithography techniques become increasingly difficult and costly as the feature size approaches 22 nm and smaller. To keep Moore's law moving forward, non-lithography techniques will become more and more important. An alternative approach to generate nanoscale patterns is directed self-assembly (DSA) of block copolymers (BCPs), which can feasibly provide highly ordered patternable morphologies such as lamellae and cylinders at a molecular level (<20 nm).
Currently, the use of DSA for generating lines and spaces utilizing conventional polystyrene-block-poly(methylmethacrylate) block copolymer (PS-b-PMMA) has shown to be in the critical dimension range of 28-50 nm pitch. A range of methods using both chemoepitaxy and graphoepitaxy pre-patterning process flows have been successful for creating both lines and spaces (lamellae) and contact holes (cylinders). In contrast, the resolution limit for single patterning 193 nm immersion scanners is 37 nm for dense lines and spaces and 40 nm for contact openings.
PS-b-PMMA has an inherent feature size limitation of about ˜13 nm because of its low interaction parameter (Chi, or χ), a fundamental measure of the block incompatibility in the BCPs. Although using multiple monomers in either block of the copolymer is not common or desired, due to potential inhomogeneity and incompatibility between the monomers, the properties of the BCP, such as χ, can be altered by the use of comonomers in either block. High-χ BCPs, which usually contain highly polar blocks, fluorine-rich blocks, or silicon-rich blocks (e.g., polystyrene-block-2-vinylpyridines [PS-b-P2VP], polystyrene-block-polydimethylsiloxane [PS-b-PDMS], polystyrene-block-poly(2,2,2-trifluoroethyl methacrylate) [PS-b-PTFEMA], etc.) are thus under intense research for obtaining 10-nm and sub-10-nm patterns. However, high-χ BCPs are generally difficult to direct and orientate their DSA morphologies due to the disparate polarities and properties between blocks. Specifically, perpendicular orientation of thin film BCP-DSA is desired for lithographical application to generate useful nanoscopic patterns on substrates, particularly for lamellar-forming BCPs. Most known high-χ BCPs cannot easily form perpendicularly orientated morphology by simple thermal annealing as does PS-b-PMMA. They need either an extra top-coat layer or solvent annealing to obtain perpendicular orientation, which can greatly increase the manufacturing cost and complication.